The purpose of this research is to investigate the neural basis for socially-mediated neuroplasticity and the integration of social information during complex decision-making using the European starling as the model system, the prevailing song culture as the social information, and female mate-choice as the decision- making task. Specifically, this research will address whether norepinephrine secretion in the forebrain mediates the effects of social information on behavioral decisions. The Specific Aims are (1) to determine the effects of social information on behavioral decision, norepinephrine secretion in the forebrain, and forebrain sensitivity to decision-eliciting cues;(2) to determine if the norepinephrine secretion in the forebrain mediates the effects of social information on behavioral decision and on forebrain sensitivity to decision-eliciting cues;(3) to determine if forebrain regions or the connectivity between them mediates the effects of social information on behavioral decision and on forebrain sensitivity to decision-eliciting cues;and (4) to determine if natural variation in social information predicts behavioral decision, norepinephrine secretion in the forebrain, and forebrain sensitivity to decision-eliciting cues. This proposal takes an integrative approach, combining analyses of behavior, HPLC, neural gene expression, and using chemical and electrolytic lesion experimental approaches. Songbirds provide an excellent model due to how well-studied the neural integration of social information (song culture) is and how feasible it is to control and manipulate social information and directly measure in a highly repeatable assay the process of behavioral decision-making (mate choice). The study will initially include a series of experiments involving controlled manipulations of social information to females making behavioral decisions, manipulations of norepinephrine secretion, and lesion experiments in which forebrain regions and connections are reduced to address the role these regions or connections play in guiding behavioral decision. This will be followed by investigating the relationships between natural variation in social information, norepinephrine secretion in the forebrain, forebrain sensitivity to behavior eliciting cues, and behavioral decision. Social organisms, such as humans, frequently make complex behavioral decisions based on recent social interactions with others, and poor integration of social information can give rise to some behavioral disorders. Because appropriate use of social information for guiding behavioral decisions often requires neuroplasticity and the formation of long-term memories, understanding the underlying neural basis for socially mediated neural integration of social information is critical. The model system used here is highly social, has social behavior that is well understood and a fundamental part of the individual's natural history, and is amenable to experimentation at the behavioral and neural level. The predicted basis for social mediation in this model involves noradrenergic systems, which are thought to be highly conserved across vertebrates.